1. Field of the Invention
The present invention relates to a signal transmission system and method, a signal adjusting apparatus and method, and a routing apparatus that are used in multi-channel digital broadcasting systems. In particular, the invention relates to a system which efficiently adjusts and routes a video signal and/or an audio signal that is included in a multi-channel television program.
2. Description of the Related Art
At present, digital broadcasting systems are proposed in which video data or audio data is compressed and coded by using the MPEG2 (Moving Picture Experts Group Phase 2) and a resulting coded stream is broadcast by ground waves or satellite-relayed waves. Such digital broadcasting systems can transmit television programs of 100 or more channels simultaneously even by using an existing transmission bandwidth because a video signal and an audio signal of each channel are compressed by using the MPEG standard.
FIG. 1 shows an example configuration of a conventional 1-channel broadcasting system. A broadcast program schedule planning section 1 generates and registers in itself a program schedule table for management of the broadcast hours of program materials that are supplied from program suppliers. Further, the broadcast program schedule planning section 1 supplies proper control commands to a program material providing section 2 and a multiplexing section 3 so that television programs will be broadcast according to the generated program schedule table.
The program material providing section 2 performs switching and image processing such as special-effects processing on a video signal and an audio signal of a television program that is supplied from an editing studio or a news studio within a broadcasting station, and outputs, to the multiplexing section 3, a program (a video signal and an audio signal) that is based on the program schedule table supplied from the broadcast program schedule planning section 1.
Based on the program schedule table supplied from the broadcast program schedule planning section 1, the multiplexing section 3 codes the video signal and the audio signal that are supplied from the program material providing section 2 according to the MPEG standard, and multiplexes encoded video and audio signals.
As described above, future digital broadcasting systems are required to transmit television programs of 100 or more channels. However, it is difficult for existing broadcasting stations to produce television programs of 100 or more channels by themselves. Therefore, it is a common practice that broadcasting stations are supplied with a plurality of program supplying companies or program producing companies.
In this case, since each program supplying company or program producing company produces television programs by using its own broadcasting equipment, the characteristics of a video signal and an audio signal that constitute a television program vary depending on the program supplying company or program producing company. The characteristics of a video signal mean its level, the gain value of its chroma component, the gain and hue offset values, etc. The characteristics of an audio signal mean the levels of the respective audio channels such as the levels of the first to fourth audio channels to which a plurality of languages (English, Japanese, and French) are assigned and the levels of the respective audio channels to which stereo sounds (right audio and left audio) are assigned, and other characteristics.
That is, a broadcasting station is supplied, from respective program supplying companies and program producing companies, with pairs of video signals and audio signals that have different characteristics. Therefore, if television programs that are supplied from the respective program supplying companies and program producing companies were broadcast to homes as they are, that is, without being modified, viewers would have a sense of incongruity when they change the channel of television programs. For example, if channels of television programs have a difference in video signal level, there occurs a problem that the brightness of a television picture varies when a viewer switches between those channels. There is another problem that the language of a sound that is output from a television receiver varies when a viewer switches the channel from one television program in which English is assigned to the first audio channel and Japanese is assigned to the second audio channel to another television program in which French is assigned to the first channel and English is assigned to the second audio channel.
An object of the present invention is to provide a multi-channel transmission system suitable for a digital broadcasting system that broadcasts television programs of many channels.
Another object of the invention is to provide a signal adjusting apparatus that modifies television programs having different characteristics that are supplied from respective program supplying companies and program producing companies into ones having common characteristics.
A further object of the invention is to make it possible to adjust television programs of a plurality of channels easily in a short time in adjusting the signal characteristics of the respective television programs.
According to an aspect of the invention, there is provided a transmission system for transmitting television programs of a plurality of channels, comprising means for receiving a plurality of source television programs supplied from a plurality of program supply sources, respectively; routing means for selecting at least one of the plurality of source television programs, and for routing the selected source television program; means for adjusting a video signal and/or audio signal included in the selected television program so that the video signal and/or the audio signal of the selected source television program and video signals and/or audio signals of the other source television programs have common settings; and transmitting means for multiplexing an adjusted television program that is output from the adjusting means with the other television programs that are output from the routing means, and transmitting multiplexed television signals.
According to another aspect of the invention, there is provided a signal adjusting apparatus for adjusting video signals and/or audio signals constituting a plurality of television programs, comprising means for receiving a plurality of source television programs; routing means for routing the plurality of source television programs, and for selecting at least one of the plurality of source television programs; and means for adjusting a video signal and/or audio signal of the selected television program so that the video signal and/or the audio signal of the selected television program and video signals and/or audio signals of the other television programs have common characteristics.
According to a further aspect of the invention, there is provided a routing apparatus for routing a plurality of source television programs, comprising selecting means for selecting at least one of the plurality of source television programs; routing means for routing television programs; adjusting means for adjusting a characteristic of a video signals and/or an audio signals of a source television signal, and for outputting an adjusted television program; and control means for controlling the routing means so that the selected source television program is supplied to the adjusting means and that the adjusted television program and source television programs that were not selected by the selecting means are supplied to multiplexing means.
According to a still further aspect of the invention, there is provided a routing apparatus for routing a plurality of source television programs, comprising selecting means for selecting at least one of the plurality of source television programs; routing means for routing television programs; adjusting means for adjusting a characteristic of a video signals and/or an audio signals of a source television signal, and for outputting an adjusted television program; monitoring means for monitoring a video signal and/or an audio signal of the adjusted television program; and control means for controlling the routing means so that the selected television program is supplied to the adjusting means and that the adjusted television program that is output from the adjusting means is supplied to the monitoring means so that a result of an adjustment by the adjusting means of the video signal and/or the audio signal of the adjusted television program can be monitored on a real-time basis by the monitoring means.